In a known fire suppression system for military vehicles one or more pressure-resistant bottles are charged with a vaporizable fire-suppressant liquid, such as bromotrifluoromethane, at a pressure of approximately 750 p.s.i.; nitrogen is used as a pressurizing agent, as outlined generally in U.S. Pat. No. 3,915,237 granted to me on Oct. 28, 1975. Outflow of suppressant from each bottle toward the expanding flame is controlled by an electrically-operated valve secured directly to the bottle. The valve can be operated by an explosive squib, as shown for example in U.S. Pat. No. 3,491,783 to Linsalato or 3,474,809 to Gordon. The valve can also be a pilot-operated solenoid valve.
The valve has an outlet that communicates directly with the target zone in which the flame is expected to occur. Alternately the valve outlet may be connected to a pipe or tube leading to the expected flame area. There are generally two types of fires to be expected, namely slow-growth fires and near-explosive fires. Slow growth fires can occur in either the crew compartment or the engine compartment, due to a variety of different causes such as leakage of hydraulic fluid or liquid fuel, loosened electrical connections, or debris accumulation. Fires of near-explosive proportions can occur when an enemy shell passes through a fuel tank in the engine compartment or crew compartment; the fireball expands rapidly within milliseconds.
In order to best contain both the slow growth fires and the near-explosive fires in different areas of the vehicle it has been the practice to use an electrical valve trigger system that includes an electronic-optical fire sensor and a manual switch (located at the driver station). The optical fire sensor provides an automatic quick-acting response to near-explosive fireballs; the manual switch provides the driver with selective response to slow-growth fires. In addition, it has been the practice to provide each bottle with a second manual valve actuation system that can be operated from a point external to the vehicle. This second manual valve actuation system comprises a cable extending from the respective valve actuator through the hull wall to a pull-type handle located on the hull exterior surface (usually located at the front end of the vehicle). The pull-type handle is to be operated when the vehicle is unoccupied at the onset of the flame (in which case the soldiers might not have time to reach the switch at the driver station), or when conditions within the vehicle dictate that the soldiers exit the vehicle before attempting to extinguish the flame.
The valves now used in existing vehicle fire suppressant systems have actuator devices that travel only very short distances, on the order of one tenth or two tenth inch, before triggering the valve element to its flow-open position. With such a very short travel it is sometimes difficult to ensure a reliable actuation of the cable system, when needed. Problems arise due to such factors as premature triggering of the valve element due to initial installation errors, in-service vehicle vibration or vehicle turn forces, and inertia forces in the cable system. Another problem relates to the user's inability to reliably ascertain whether the valve is actually open; when the soldier exerts a pull action on the handle of the cable he is never quite certain that the very slight resultant handle movement has opened the valve or has merely taken up slack in the cable system.
The present invention is directed to a remotely-actuable cable system for a fire extinguisher valve, wherein the cable is subdivided into two separate cable sections joined together by a lost motion connection. The use of such a lost motion connection is advantageous in that it magnifies the motion required at the handle compared to the motion experienced at the valve actuator. For example, if we assume a lost motion of nine-tenth inch, then a one-tenth inch valve actuator motion requires a one inch handle pull motion. The user is able to accelerate the handle through a one inch motion distance and receive sensory feedback of a perceptible motion.
The lost motion connection envisioned by applicant preferably includes a compression spring arranged to exert a progressively increasing force on the valve actuator as the manual pulling force is applied to the handle at the outer end of the cable. The spring force and spring rate are selected so that the valve is actuated to the flow-open position before the handle reaches the full limit of its motion. Therefore, the user is certain that the valve is actuated even though the handle is not pulled through a complete stroke. Also, since a significant movement of the cable is necessary to actuate the valve there is a lessened likelihood that vehicle vibrational forces will prematurely trigger the valve to the flow-open condition.